The invention provides a method and device for determining a fault point location of a neutral point non-effective grounding system. The determination method comprises the following steps that whether or not a line in the neutral point non-effective grounding system has a single-phase grounding fault is determined; if the single-phase grounding fault occurs, a circuit breaker of a control line will close again after a first trip; if the re-closure of the circuit breaker fails, a permanent fault of the line is determined; if the re-closure of the circuit breaker is successful, an instantaneous fault of the line is determined; under the condition that the permanent failure of the line is determined, a control circuit breaker is trips again; the re-closure time of the circuit breaker and the arrival time of reflection waves at the single-phase grounding fault point of the line after the circuit breaker trips again are obtained, and the location of the single-phase grounding fault point of the line is determined according to the re-closure time and the arrival time of the reflected waves. By the technical scheme, the fault type can be determined, and the fault position can be further detected accurately when the fault type is a permanent fault.